Bug reports are extremely useful to improve the quality of the software, you should consider reporting every bug you find.
Include as much information as possible to help reproduce the defective behavior. A standard way is to explain step by step the chain of actions that leads to the issue.
You should also include information about your system (version of Windows, 32 bits or 64 bits, etc.)
Kinovea has two types of logs files, the main log and the "unhandled crash" logs, they are also very useful to understand what went wrong.
Note: the main log file already contains information about your system and Kinovea version.
You will find them in the Application Directory.
You can open this folder from within the program itself through menu Help > Open log folder.
Note: the main log is erased each time Kinovea launches. In order to collect useful logs, you need to make the problem appear just before copying them.
Copy the log.txt and whatever "Unhandled Crash" logs there might be and include them as attachment in the bug tracker along with the problem description.
If for whatever reason Kinovea doesn't even start, you will find the log folder here:
Under Windows XP:
C:\Documents and Settings\[your user name]\Application Data\Kinovea
Under Vista or 7:
C:\Users\[your user name]\AppData\Roaming\Kinovea